Sep 21 2011

Shortening the Firing Time – Follow-Up

There have been a lot of responses and questions about my last posting about shortening the firing time and I’d like to address them here.

First, I must say that I’ve never gone back to firing the first phase in the kiln. Firing on a camping stove, kitchen stove, or the SpeedFire® Cone System™ for Metal Clay seems to work 100% of the time. The advantages:

1. It saves a lot of time. The firing time is practically the same as firing silver clay.
2. You don’t need to worry whether you held long enough at the first phase. When the smoke is gone and the pieces darken, you can be sure that the binder has burned off completely.
3. No need to cool down between phases.
4. In a workshop situation, a lot more pieces can be fired.

Again, this way of firing replaces the first phase only. Once the binder has burned off, the pieces need to be covered with carbon and the box should be moved to a kiln for the second phase.

It’s been reported that an electric kitchen stove works just as well. It makes sense: when the pieces are not covered in carbon, the binder will burn at 400-500F, which is within the capacity of an both electric and gas stoves.

As a lid you can use just a fiber board or fiber blanket with a hole These photos were missing from my last posting.

Top view

Fiber blanket

Watch for the smoke coming out of the hole. If you are not sure (sometimes thin pieces don’t generate a lot of smoke), it is ok to remove the lid with a glove or tweezers to look for the smoke and the color of the pieces.

I have successfully fired big and hollow pieces, including rings. My advice: with complex pieces use low heat; it’s best for the binder to burn out slowly. Still, the firing time rarely exceeds 10 minutes. (Rings need to be positioned in a special way. I will talk about it in my upcoming workshops).

And finally – this works with all base metal clays: bronze, Rose Bronze, White Bronze, copper, and steels.


Sep 14 2011

Pre-Conference Class on Mokume-Gane Band Rings

At the PMC Guild conference in July 2012 I will be teaching a class and giving a presentation.

The Class

On June 19-20 I will be teaching a 2-day workshop on making mokume-gane band rings from metal clay as part of the PMC Guild pre-conference classes. We will practice a few mokume-gane designs. Some of the designs are covered in my latest book, Patterns of Color in Metal Clay, but require some modification when applied to rings. Other designs are new developments. In the workshop we will also cover the firing process for base metal clay in depth, as well as sizing rings and finding solutions to possible reactions between the metal and the skin.

You can sign up for the class on my website. Please have a look at the toolkit required for the class, and email me if you have any questions. Please order clay prior to the class and bring it with you. You can order the clay, a finishing kit, and books on my online store. Since I will be flying in, I will not be able to bring books for sale.

Here are some class samples.

Woodgrain

Woodgrain 2

Veins

Veins 2

Storm

Steel and Silver Lining

Table

Eyes

Condensing

Carving

Cabs

The Presentation

In the conference I will also give a presentation on ways of combining different metal clays. The presentation will cover the nature of metal clay jewelry as opposed to cast and fabricated ones, the sintering process, and ways of combining different metal clays together to create mixed metal pieces of jewelry. I will discuss and illustrate which metals clays can be fired with others and under what conditions. If you are interested, please sign up through the PMC Guild.


Sep 13 2011

Shortening the Firing Time

While experimenting with firing in more efficient ways I discovered something that can shorten the firing time significantly. It seems that the first phase – in which the binder is expended – does not have to be done in a kiln and can be completed in as little as 10 minutes, with no cooling time between phases.

This can be done with the SpeedFire Cone system, on a camping stove, or on the kitchen stove.

Here is how it works:

Pour a 1″ layer of carbon into a small stainless steel bowl. Place your pieces on top of it without covering them in carbon.

Put the bowl on the burner.

Cover the bowl. You can use the cone from the cone system, or the circular fiber box that is actually a firing box, or a fiber board, or a piece of fiber blanket. If you use the cone, cover it with a fiber board or a fiber blanket.

In each of these lids drill a pencil-size hole. To do this in a fiber board or the fiber box you can use a screwdriver. Just twist it in; the fiber is very soft. With the fiber blanket just stick in a pencil to make the hole.

Here are some photos of the set-up:

Fiber board with hole on top

This photo was taken inside my studio, but this should be done outdoors.

Set-up

On the left is the fiber box; on the right is the fiber cone. The pans are flat, but I mostly use simple bowls.

Kitchen

If you do this in the kitchen, the fiber blanket is not recommended. You can protect your stove with aluminum foil.

Turn the flame on to full capacity. After a few minutes you will smell and see the smoke coming out of the holes in the lids. This is the binder burning. I tried to photograph it, but it turns out that smoke and fire are hard to shoot.

After about 10 minutes the smoke will stop. Remove the lid with a glove and peek inside. The pieces should look black.

Before

After

Pour more carbon into the bowl to cover the pieces and put them in the kiln for the second phase of firing. The whole process takes about 2:30 from beginning to end.

I have just fired a batch of thick pieces. If I had done the first phase in the kiln, I would have had to hold for at least 2 hours. Given that the ramping takes about 30 minutes and the cooling time at least on hour, I saved myself 3:30 hours.

Why not burn the binder with a torch?

I have tried this many times. The pieces were positioned the same way, in a bowl with a 1″ layer of carbon. This works only sometimes. In most cases pieces crack from the direct heat, and the cracks do not necessarily show until after the second phase is over.

Why not do the same thing in a kiln?

I have tried this as well. A kiln takes a long time to ramp. This exposes pieces to oxygen for an extended length of time and most probably causes internal oxidation. That means that when they come out of the kiln after the second phase, they may crumble, but not necessarily because they are not sintered: it’s because they are oxidized.

Why is the fiber cone or box necessary?

Without them, it would take a long time for the pieces to heat up and they might oxidize, just as in a kiln. The fiber cone and box create a hotter chamber, partially shielded from oxygen.

A word about internal oxidation: before the advent of base metal clay, I used copper pipes, rods, and wire (solid, or bare, copper, from plumbing supply stores). I used to wrap them with silver clay (low shrinkage) and fire. Cracks would occur because of the shrinkage of the silver, and I had to repair and re-fire. Nothing in the way that the copper looked showed any sign of oxidation. However, after a few repairs, the copper would crumble in my hands.

This is one of the reasons that I avoid firing copper in open air. Even if it looks fine after firing, you never know what is going on inside. Furthermore, sometimes the copper needs to be re-fired, as in repair, enameling, soldering, or adding silver clay. With each firing the copper oxidizes further and weakens, just like what happened with the solid copper.


Sep 8 2011

Notes About Upcoming Classes

I just wanted to post a few notes about my upcoming classes:

1. A spot has opened up at my workshop in Tuscon, AZ on January 28-30 and there are 2 spots left for January 30. Please contact:

Lyle Rayfield
Art Jewelry & Instruction
Tucson, AZ
520-682-8325

bdangled@dakotacom.net

Here is Lyle’s website.

2. The pictorial/architectural intensive at my studio in January 7-11 is filling up. Please contact me if you would like to participate. You can see the class description here.

3. The next travel-teaching class after Tucson will be on April 20-22 at PMC Connection in Dallas. You can sign up as soon as it is posted on their website.